Separation of oil-wax mixtures



April 23, 1935. l. M. PERKINS vEr Al.- 4 1,998,464

SEPARATION OF OIL WAX MIXTURES Filed July s, i931 Mi Wax zwerver/'r Ivan 10er/Z291.;

raser-00o)- Patented Apr. ze, 1935 j 1,998,464

UNITD lsmrrs PATENT ori-'ICE SEPARATION or Olm-WAX Mix'rmms Ivan M. Perkins, Brookline, and Stewart S..Kurtz, Jr., Merion, Pa., assignors to The Atlantic Refining Company, Philadelphia, Pa.,\a cor,- poration of Pennsylvania Application July 3:1931, serial No'. 548,674

'6 Claims. (Cl. 19d-20) .The present invention relates to the separation operation, thoroughly agitating the mixture. This of a mixture of wax and hydrocarbon oil into its procedure, Which in each CaSe iS PiOpelly regrespective solid and liquid components, and more ulated to the particular Oil-WRX mixture being particularly to the treatment of that type of oiltreated, results in the formation of distinct age 5 wax mixture which is adapted to be separated glomerates, each f Which may be the SiZe 0f 5 into such components by the well known process grains Of rice, 01 0f that Order, 0I SOmeWhuii of sweating. larger, for example, of the size of peas. Such Typical of those oil-wax mixtures which are agglomeraties muy the!! be redilYSePalated fiOm adapted to be subjected to a process of sweating that pOliiOn 0f the miXiuie Which TemaiIlS liqlo and therefore adapted to be treated by our procuid, by any Suitable mei'fhOd ada-Died 130 the Sep- 10 ess, is the Wax cake, commonly known as slack i'atiOIl 0f SOlidS from liquidS, 2S fOi' eXdmPle, by wax,which remains in the filter press when petrodraining the liquids fIOm the S0lidS We hui/e leum fractions, such as those known as pal-anim found that agglomerates so formed entrain or ocdistillates, are subjected to a pressing operation. elude Very little., if'any, 0f that DOIiSiOn 0f the Such oil-wax mixtures usually contain less than mixture which remains liquid during their forma- 15 50% of oii. tion. By treating the .agglomerates so formed Asis well recognized, sweating processes require One or more times, for example, under SUCCESS" prolonged periods of time, large and cumbersome iVelY higher temperature COIldiiiOnS, a Series 0f apparatus, and the utilization of considerable Solids of progressively higher melting points may 0 heat. An object of the present invention, which be DIOduCed- Thus by Our IJIOCBSS a Substantially 20 is based upon an entirely different principle from oil-free Wax may be Produced ond/o1' there 'may that upon whichsweating is bsed, is to replace be effected a fractional separation of the solid sweating, thereby to overcome, among others, Components of an oil-Wax mixture into two or the objections above stated. By our process, oilmore fractions of dfleronl" melting ponts- 5 wax mixtures of the type aforesaid may be sep- Hereinafter, for convenience, the term "wax 25 arated eiciently, economically and rapidly into Will be used to ,indicate that material which forms their respective solid and liquid components. aS a Solid during the agglOmeIa'iIig Step 0f Our Furthermore, our process and apparatus are ca- Process, and the term oir Will be ilsod to indi'- pable of separating a composite wax mixture into Cate that material which remains liquid during a series of wax fractions of progressively higher and immediately after Snell Stop It iS t0 be uIl- 30 melting points. derstood, however, that in some cases, depending If an oil-wax mixture is completely liqueed, uDOn the particular Operating COuditiOnS and/01 then maintained in a static condition and cooled, ille'metelials 01' mixture being treated, W113i may those components thereof which become solid as be Called Qill1e1eiu, ill fat may be liquid Wax.

a resun of the coming-form as one urge mass A preferred ferm 0f our apparatus for carrying 35 or cake which occludes substantial quantities of 01111 the PIOCeSS CGIISSS in a COIlduiii llOliZOIliefllY .those components which under prevailing condimounted having an OVeIlOW pipe at 011e end and tions are still liquid; the solid components, in COmmuniCaffing With 2' Supply tank located adforming, apparently becoming so interwoven as jacent the Opposite end S0 that the lidueed Oil- 40 to prevent substantial vmovement of the liquid Wax mixture to be separated may be introduced 40 components occluded therein. It is well known into the conduit. Our apparatus in its preferred that if such a solid mass is comminuted, it will form also hasA chambers disposed beneath each become of a more or less liquid consistency, preend of the conduit. The chamber below the outsumably because the occluded liquid components let end of the conduit has an opening for admitare then free to move. The present invention, ting cooling liquid thereinto. The chamber at 45 however, is not based upon nor`does it include its opposite end has at least one, and usually, any step of comminuting a previously solidified two outlets for conducting the cooling liquid from oil-wax mixture. the conduit. The conduit is provided with agitat? l According to our invention, the oil-wax mixture ing means for maintaining the oil-wax mixture 0 is first lised to a temperature sufcient to comand the cooling liquid in intimate contact during 50 pletely liquefy the solid portion thereof; therecountercurrent passage therethrough. upon the mixture in a completely liquid state is The primary factors upon which the success of uniformly'cooled .to a temperature at which at the process depends are: (l) control of the temleast a portion thereof will solidify, while simulperature 'during thecooling step of our process;

5a taneously and continuously, during such cooling (2) the rate of agitation during the cooling step; 55

lil

3) the detergent characteristics of the cooling liquid; and (il) the diiference in specific gravity between the cooling liquid and the liquid oil-wax mixture. The optimum rate of cooling and degree of agitation may vary depending upon the particular oil-Wax mixture being treated. A given oil-wax mixture, if cooled too rapidly or shockechilled, may not produce the desired solid agglomerates. The usual effect of cooling too rapidly or shocl-chilling the oil-Wax mixture is the formation of that portion thereof which becomes solid into a fibrous mass. quite unlilse the distinct agglomerates formed by our process which may be easily separated from the portion of the mixture which remains liquid. Cooling too slowly causes that portieri which solidies to form as very small particles from which the liquid portion is difficultly removable. While the particular specific gravity of the cooling liquid is not a significant factor in causing agglomerates of a certain size to form, yet it is a factor of importance in operation; that is, the greater the difference in specific gravity between the cooling liquid and the oil-wax mixture being treated, the more complete will be the separation between the liquidand the mixture.

As regards agitation, if the mixture is agitated too slowly during the cooling step, the desired formation of agglomerates does not occur, but, on the other hand, that portion which becomes solid forms as a mass in which substantial quantities of the portion which remains liquid are occluded; whereas when the mixture is too vigorously agitated during the cooling operation the desired agglomeration is not effected, since the solids form as minute particles from which it is difficult to separate that portion of the mixture which remains liquid. Agitation in accordance with our process is such as to cause that portion of the mixture which becomes solid during our agglomerating step to form as distinct aggregates or agglomerates of the size of grains of rice, or of that order, or even larger, as for example, of the size of peas. Herein, and in the appended claims, the term thoroughv as applied to agitation will be used to indicate an intensity of agitation suflicient to cause this desired formation of agglomerates.

The preferred form of the apparatus herein described Ais an improvement over vertical type crystallizers disclosed in a copending application filed jointly by one of the present applicants and another inventor. It was found that with certain oil-wax mixtures treated in the vertical type crystallizer there was a tendency for the cooled solidified particles to settle from the top of the crystallizer. This in some cases necessitated a vigorous agitation which led to emulsion'troubles. By passing such oil-wax mixtures through the preferred modification of our apparatus herein disclosed, the cooling liquid is passed horizontally in countercurrent direct heat exchange contact with the oil-wax mixture with proper agitation. The immiscible cooling liquid, being heavier than the oil-wax mixture settles therefrom when allowed to stand, but such liquid is kept in intimate contact with the oil-wax mixture during passage through the central portion of the conduit by means of agitating blades affixed to a rotatable shaft. It is found that in the separation of an oil-wax mixture into its components, emulsion troubles are eliminated by employment of our invention.

In some cases, especially wherel the difference in specific gravity between the oil-wax mixture Locatelli and the cooling liquid is small, it may be desirable to elevate the end of the conduit at which the treated oil-wax mixture overflows, thereby to effect a better separation between the oil-wax mixture and the cooling liquid. An elevation of about 10 is in many cases desirable. However, any suitable angle of elevation to the horizontal is within the spirit and contemplation of this inu vention.

Wax leaving the conduit may be separated from the accompanying oil and small amounts of cooling liquid by draining, spraying with water or a detergent liquid, or by immersing the wax in a liquid and removing it therefrom by screening means.

While the wax products which result from operation of our invention have a substantially higher melting point than the respective oilwax mixtures from which they are produced, it is possible to rerun these wax products several times to obtain waxes of increasingly higher melting points. In each case, it is preferred to reduce 'the temperature of the molten oil-wax mixture in the conduits to at least 10 F. below the melting point of the original mixture. .Too great a reduction in temperature causes solidication` to an undesirable extent of the higher melting constituents; but we have found that it is possible to obtain good results with a reduction of, for example, about 25 F. below the melting point of the oil-wax mixture being treated.

For a better understanding of our invention, reference is had to the accompanying drawing which represents an elevational view, partly in section, of a preferred form of our apparatus.

In the drawing, I represents a crystallizer cornprising a horizontal conduit 2 having a downwardly extending end chamber 3 connected therewith at the feed end of the crystallizer. The crystallizer may have a downwardly extending chamber 4 at the opposite or wax outlet end of the crystallizer into which chamber cooling fluid may be admitted. A shaft 5 is longitudinally mounted within the conduit 2 and has agitating blades 6 rigidly affixed thereto, and extending to a point adjacent the inner surface 4'of the conduit. One end of the agitator shaft is journaled in the wall above end chamber 4 in bearing l; while the other end of the shaft extends through the wall above 'end chamber 3 at point 8, and is driven by any suitable means through gear 9.

Molten oil-wax from supply tank I0 is transferred through line Illa into the feed end of the crystallizer at a suitable rate of flow, controlled by valve Ilb in line Illa, and passes through the crystallizer toward overflow spout or trough I6; such passage is assisted, if desired, by adjusting certain of the agitator blades 6 to get a pushing effect toward the outlet end of conduit 2.

A cooling liquid, which, for example, maybe a sodium silicate solution, is pumped from tank I I by pump P and is transferred through pipe I2 controlled by valve I2 into the lower part of end chamber 4 (or in the absence of end chamber 4, into the lower part of the conduit 2 at the outlet end) prior to the introduction into the chamber or conduit the liquid is reduced to the .,esired temperature by passage through cooler C. Upon reaching the lower level of conduit 2, the cooling liquid ows by gravity toward end chamber 3 in countercurrent direct heat exchange Contact with the molten oil-wax mixture and finally settles into end chamber 3.

Pipe I3 controlled by valve I3 taps the'cooling liquid from the lower portion of end` chamber 3,

vcountercurrent to each other.

and connects with line I3a controlled by valve I3b winch transfers the liquid by gravity back into tank II. Flow of cooling liquid through the crystallizer is thereby made circuitous.

The ow of cooling liquid may be effectively controlled by replacingor supplementing pipe I3 by an adjustable overflow pipe I4 connected to the lower portion of chamber 3, and emptying the overflow spout I6. Rotation of agitator shaftr 5 is then commenced, and the rate of rotation is increased tojsubstantially R.- P M., for example. While the molten cil-wax is agitated, precooled silicate solution at a temperature slightly lower than that tov which it is desired to reduce the oil-wax mixture is pumped into end chamber 4, as described heretofore, and upon risin above the bottom of the conduit 2, flows by gavity toward end chamber 3. Agitator blades 6 extend almost to the bottom of conduit 2, and in rotating intimately intermix the molten oil-wax and the cooling solution, thereby providing a thorough heat exchange contact; thus it may be said that the oil-wax and the cooling solution flow in a homogeneous, uniformly disseminated condition When the oilwax mixture arrives at the nish end, i. e., the end above chamber 4 ofthe crystallizer, it is at the desired temperature,.for instance, about 80 F. when a wax having a melting point of F. is being produced, and overows through the spout I6; At the same time molten oil-wax mixture from supply tank III is continuously fed into the crystallizer above end chamber 3 at a suitable rate. As this molten oil-wax progresses toward the nish end of the crystallizer in intimate contact with and countercurrent to the cooling liquid, its temperature is slowly and evenly reduced to a temperature at which at least a portion of the wax solidies. The wax content solidies as small particles, probably crystalline, and the thorough agitation alforded by agitating blades l causes the small particles to agglomerate into compact wax masses which are substantially free from oil. Upon reaching the nish end of the crystallizer, substantially all of the wax which solidies at the reduced temperature is agglomerated.

If the agitation is too slow, agglomeration does not occur. On the other hand, extremely vigorons agitation seems to have a tearing action which prevents or materially hinders agglomeration. Regulation of the rate of agitation makes it possible to control, within limits, the size of agglomerates. Rate of agitation and rate and extent of temperature reduction may be adjusted to suit particularoperating conditions.v There being no agitation in the lower part of end chamber 3, the mixture of oil-wax and cooling fluid rapidly separates to form a more or less definite interface with the oil-Wax, the heavier cooling fluid settling to the bottom of the chamber. Adjustment of the height of the point of discharge of the overflow pipe Id determines the level of this interface, a desirable level being an inch or so below the bottom of the conduit 2. The cooling huid which separates into the lower part of end Achamber 3 has, due to its contact with the molten oil wax, been increased in temperature, for example, to 102 F. By constant addition of molten oil-wax and cooling fluid, and by suitable adjustment of the overow pipe I4, th e ratio of oil-wax to cooling iluid is maintained, and cooling fluid continuously ilows from chamber 3 through pipe I4 and treated wax is continuously discharged from conduit 2 through overflow spout I6. A certain amount of cooling fluid is passed out through spout I6 with the treated wax to make its separation from adhering oil easier,

the amount of uid so overilowing being adjustable by regulation of the agitation adjacent the ,overflow spout. Y

In accordance with the separating device shown herewith by way of illustration, the overflow mixture passing from spout I8 entersonto .endless perforated belt `20 which is mounted within the separating vessel 2I. l The belt is driven in a clock-wise direction by rollers 22 and 23 within they separator vessel 2|, which rollers are in turn driven by any suitable means, not shown; and near the forward end of the path of travel of the endless belt, is mounted partition 24 which divides the vessel 2l into an oil compartment 25, and a wax compartment 26. lAs the overflow mixture travels -with the endless belt, the liquid portions thereof, i; e., the oil andcooling fluid, gravitate throughthe perforations in belt 20 into oil compartment 25. To assist in a Athorough separation of the liquid portions from the wax, the overflow mixture is sprayed with washing liquid in a cooled condition from perforated pipe 21 which is mounted above the endless belt 20. Pipe' 21 is supplied with washing liquid from tank II through pipe 28 controlled by valve 28', by means of pump P. It is necessary to keep the temperature of the overflow mixture sufficiently low so that the agglomerated wax content thereof will not melt while passing along the belt 20. Cooler C' surrounding a portion of pipe 28 is employed to reduce the temperature of the washing liquid to the desired extent before the latter is sprayed onto the over w mixture on belt 20. The washing liquid and vooling fluid may be the same material to assist in the subsequent separation of oil therefrom.

The liquid portions of the overflow mixture and the washing liquid gravitate into compartment 25 and separate therein into a homogeneous lower layer containing the cooling and washing uids and an upper oil layer. The former is tapped from the bottom of the vcompartment and re turned to tank II by pipe 29 controlled by valve 29', while the supernatant oil layer is drawn off through pipe 30 controlled by valve 30'.

Agglomerated wax passed into compartment 26 from the forward end of the path of travel 'of the endless belt 20 may be melted-by steam, and coil 3i for passage of steam is provided for -such purpose. The molten wax may then be drawn off ,to storage; or in case it is not desired to melt the wax pellets, they may, for example, be received fully inustrate our process.

Example 1.-A slack wax melting at 105 F. was

heated to F. and run through a horizontal crystallizer of the type above described. A 2% solution of sodium silicate in water was passed into the nish end of the crystallizer at 80 F., and drawn from the feed end atri F. The oppositely iowing slack wax and silicate solution were thoroughly agitated while in mutual contact in the crystallizer, and as a result, a mixture containing molten oil, agglomerated Wax and a certain amount o silicate solution overflowed from the crystallizer at a temperature of 82 F, After draining and spraying this overflow mixture, a wax product `was obtained having a melting point of 112.2 F., representing 69% of the original slack wax.

Example 2.-The waxvproduct obtained in Example l was heated to 130 F., and passed through the horizontal crystallizer. Its temperature at the ov eriiow end of the crystallizer was reduced to 1009 F. The agglomerated wax was' freed from the liquid constituents of thecharge and from the silicate solution which had overflowed from the crystalizer, and was found to have a melting point of 119 F. This product represented 59% of the charge. Y

Example 3.-A slack wax melting at 104.5 F. was treated as in Example 1, and a wax product melting at 110 F. was obtained, which represented a 62% yield. On rerunning as in Example 2, a wax product melting at 125 F., andrepresenting 36% of the charge was produced.

By operation of the horizontal, or inclined crystallizer in accordance with our invention, wax particles may be produced which are harder and more free from oil than wax particles resulting from treatment of va similar crude wax in a vertical type crystallizer. This additional hardness and freeness from oil is significant in putting out a wax in the form of rice, which will not stick together at ordinary temperatures. Also, the wax produced in accordance with our invention is more easily and completely freed of adhering oil which is an advantage regardless of the form in which the wax is finished.

The rate of rotation of the agitating blades may be controlled solely on the basis of its eifect upon the size of agglomerates, and need not be rotated more rapidly to prevent settling of the wax as is sometimes necessary when a vertical type crystallizf-r is employed.

What we claim is:

l. A process for separating the higher melting constituents from an oil-wax mixture which is adapted to be sWeated, which comprises melting the oil-wax mixture, contacting an approximately horizontally traveling body of the molten oil-wax mixture with a countercurrent body of cooling 'liquid substantially immiscible with the oil constituent of the mixture and of a specific gravity sufficiently different so that it readily stratifles, whereby the molten mixture is cooled to a ternperature at which at least a portion of the wax content thereof crystallizes, thoroughly agitating said mixture 'while cooling, whereby the crystallized wax combines to form a plurality of agglomerated wax masses, and separating said agglomerated wax masses from the liquid oil.

2. A process for separating the higher melting constituents from an oil-wax mixture which is adapted to be sweated, which comprises melting the oil-wax mixture, intermingling an approximately horizontally traveling stream of said molten oil-wax mixture with a countercurrent stream of a cooling liquid immiscible with said oilwax mixture and having a different specific gravity therefrom, whereby said molten oil-Wax mixl Leashes ture is cooled to a temperature at which at least a portion of the higher melting constituents thereof crystallize, thoroughly agitating the oilwax mixture during cooling, whereby the crystallized higher melting constituents combine into a plurality of agglomerates," and separating said ag,- glomerates from the constituents of the oil-wax mixture which remain liquid and from the cooling liquid. y

3. A process for separating the higher melting constituents from an oil-wax mixture which is adapted to be sweated, which comprises passing a horizontally traveling body of molten oil-wax mixture in countercurrent heatexchange direct contact with a cooling liquid substantially immiscible with said oil-wax mixture and having a different specific gravity therefrom, whereby said oil-wax mixture is cooled to a temperature at which at leasta portion of the highermelting constituents thereof crystallize, agitating said oil-wax mixture while cooling to cause said crystallized constituents to combine into a plurality of agglomerates, and separating said agglomerates from the constituents of the oil-wax mixture' which remain liquid and from said cooling liquid.

4. A process for separating the higher melting constituents from an oil-wax mixture which is adapted .to be sweated, which comprises passing a continuous substantially horizontally traveling stream of molten oil-wax mixture in countercurrent heat exchange direct contact with a cooling liquid immiscible with said oil-wax mixture and having a different specic gravity therefrom, to slowly cool said molten oil-wax mixture to a temperature at least between 10 and 25F. below the melting point thereof, whereby at least a portion of the higher melting constituents of the oil-Wax mixture crystallize, thoroughly agitating the oil-wax mixture while cooling, whereby the crystallized constituents combine to form a plurality of agglomerates, and separating said agglomerates from the constituents of the oilwax mixture which remain liquid and from the cooling liquid.

. 5. A process for separating the higher melting constituents from an oil-Wax mixture which is adapted to be sweated, which comprises progressively cooling a horizontally traveling body of molten oil-wax mixture by direct contact with a cooling liquid having a progressively lower ternperature, thereby reducing the temperature cf said molten oil-wax mixture to a temperature at which at least a portion of the higher melting constituents crystallize, thoroughly agitating said mixture during the cooling step, whereby said crystallized constituents combine to form a plurality of agglomerates, and separating said agglomerates from the constituents of the oil-wax mixture which remain liquid and from said cooling liquid.

6. 'I'he process for separating the higher melting constituents from an oil-wax mixture which is adapted to be sweated, vwhich comprises passing an approximately horizontally traveling stream of molten oil-wax mixture through an elongated zone in direct countercurrent heatexchange contact with a cooling liquid, immiscible with and of a higher specific gravity than said oil-wax mixture, whereby the molten oil-wax mixture is cooled to a temperature at which at least a portion of the higher melting constituents thereof crystallize, th Jroughly agitating the oil-wax mixture while cooling and passing through said zone, whereby the crystallized constituents combine into a plurality of agglomerates, allowing the cooling uid and occluded oil to ow into a second zone, said second zone communicating with the end of the elongated zone adjacent tiie point at which molten oil-Wax mixture is introduced tliereinto, and being located at a lower level than the said elongated zone and being substantially free from agitation, whereupon the said cooling ud settles to the bottom of said second zone from which it is removed,

and oil gradually rises and again is drawn into said elongated zoney withdrawing oil and wax agglomerates from the opposite end of said elongated zone, and separating said agglomerates from the constituents of the oil-wax mixture which remain liquid.

IVAN M. PERKINS. STEWART S. KUR'IZ, JR. 

